17 TC 125 cutting out

dtl210
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9/21/2018 7:06pm
Street test is much better but still not perfect. I'll throw it in the trailer. 18 yz450 is reliable as can be if the husky doesnt run.

Thanks for all the help everyone! Hope we're close to done!
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CarlinoJoeVideo
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9/21/2018 9:23pm
dtl210 wrote:
Street test is much better but still not perfect. I'll throw it in the trailer. 18 yz450 is reliable as can be if the husky doesnt...
Street test is much better but still not perfect. I'll throw it in the trailer. 18 yz450 is reliable as can be if the husky doesnt run.

Thanks for all the help everyone! Hope we're close to done!
The new power valve arms might be the answer. Less oil in your premix could help it all from gumming up maybe?
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BR8ES
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9/22/2018 5:23am
FWIW, I ordered the F1 arms a little over a week ago and tracking shows today for delivery.
1
9/22/2018 11:14am
BR8ES wrote:
FWIW, I ordered the F1 arms a little over a week ago and tracking shows today for delivery.
I ordered the f1 arms. Night and day difference. And shipping was faster than I thought. 7-8 days.
1

The Shop

BR8ES
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9/22/2018 12:56pm
BR8ES wrote:
FWIW, I ordered the F1 arms a little over a week ago and tracking shows today for delivery.
I ordered the f1 arms. Night and day difference. And shipping was faster than I thought. 7-8 days.
Excellent and I was surprised at the shipping. Still prepping my 19, May as well put them on. Cheap too.
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garagedog
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9/22/2018 9:26pm
Base gasket and cylinder Orings are super cheap. Order them all.
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dtl210
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9/24/2018 4:55am
Well the bike still runs like dog shit, might have gotten even worse. Angry Will order the f1 arms, gaskets, orings and anything else I can think of today.
dtl210
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9/24/2018 4:17pm Edited Date/Time 9/24/2018 4:23pm
Is there a chance one of your jets are clogged?
I considered that also. Jets are new and I've swapped quite a few in and out with no change in the bog so I don't think so. However I plan to do a full re-built / cleaning of the carb before the f1 arms show up.

Edit:
There was another 18 125 at the races, man it sounded good and looked fun. Hope I get there someday soon.
BR8ES
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9/24/2018 6:20pm
Just make sure you have someone to sign for the package, I missed the delivery and picked my F1 arms up today from the post office. Hope you get your bike sorted, bet you will once the top end is pulled and redone with orings and such.
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dtl210
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9/25/2018 10:44am
As I wait on parts...

Has anyone experienced electrical issues on these bikes? My neighbor who is an ex-mechanic thinks that I have a CDI or stator going bad. Is there a repair manual for these things that explains how to test the electrical system? The "user" manual is pretty useless.
BR8ES
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9/25/2018 11:55am
Very rare to hear a CDI going bad, maybe the stator.These other guys will add more to this than me however.
DynoDan22
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9/25/2018 12:25pm
Usually a stator will start breaking up in the upper mid to top end revs. Not to say that you don't have an electrical problem, but it's unlikely. The sound you bike was making sounded more mechanical like a powervalve issue or piston/cylinder issue as the sound it was making was right at the rpm when the powervalve was going to open. Maybe take the powerval side covers off, start the bike and shoot a video to see if you can replicate the gurgle on the stand.
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dtl210
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9/27/2018 5:56pm
Here is a video of how the powervalve moves when I rev it on the stand. It appears the bog happens when thr pv is fully open?
It's hard to say since I can't do much street testing but I swear it gets worse as the bike gets warmer. It seemed way worse after a few laps on the track.

https://youtu.be/6hnXCpNkDRM
CarlinoJoeVideo
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9/27/2018 9:14pm
dtl210 wrote:
Here is a video of how the powervalve moves when I rev it on the stand. It appears the bog happens when thr pv is fully...
Here is a video of how the powervalve moves when I rev it on the stand. It appears the bog happens when thr pv is fully open?
It's hard to say since I can't do much street testing but I swear it gets worse as the bike gets warmer. It seemed way worse after a few laps on the track.

https://youtu.be/6hnXCpNkDRM
Man, I was 100% with everyone thinking this was a mechanical problem but you might want to start swapping electrical parts with someone who has a KTM or husky. Watching the PV and hearing that sounds VERY odd!

Could it be a carb issue?
Bad gas?
Maybe do a compression check?
dtl210
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9/28/2018 4:50am
Man, I was 100% with everyone thinking this was a mechanical problem but you might want to start swapping electrical parts with someone who has a...
Man, I was 100% with everyone thinking this was a mechanical problem but you might want to start swapping electrical parts with someone who has a KTM or husky. Watching the PV and hearing that sounds VERY odd!

Could it be a carb issue?
Bad gas?
Maybe do a compression check?
I may have to reach out to the previous owner to swap parts.
I'll go through the carb again this weekend, compression feels strong but I dont have a tester, I drained the gas that came in it and replaced it with fresh non-ethanol.
Gaskets should be here today so I can measure ring gap, clean powervalve and check deck height.

Wish I could find a service manual to check the stator. Really starting to lean towards electrical since it seems to get worse as heat builds.
DynoDan22
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9/28/2018 7:20am
That powervalve seems to be opening way too soon. Did you adjust the powervalve adjuster at all??
dtl210
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9/28/2018 7:26am
DynoDan22 wrote:
That powervalve seems to be opening way too soon. Did you adjust the powervalve adjuster at all??
Yes, the it is at 2 turns in from full out right now which seems to be where most people run them. I've been as far as 4 turns in, adjusting the PV just moves where the bog happens.
dtl210
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9/29/2018 10:43am
So for the test shown in the picture, I'm getting a reading of 32. Slightly outside of the spec. Is that enough to warrant replacing the stator?
AJ565
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9/29/2018 3:12pm
What is the temp that you're testing it at? The resistance can go up or down depending on temp. Also make sure your leads read 0ohm when touched together.
AJ565
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9/29/2018 3:15pm Edited Date/Time 9/29/2018 3:16pm
Just watched the video. Sounds like jetting to me. This is the jetting we've found works well in a '18 150 so it should get you in a better direction.

Pilot 30
470 main
slide 5.5
needle 42-71 3rd clip from a 2019.
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dtl210
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9/29/2018 3:16pm
About 65 degrees. Took it down the street and tested again, it was at 37.

Have the jug off now. Piston looks good, powervalve is clean as can be. Going to reassemble with new orings and wait for the f1 arms to show up.
CarlinoJoeVideo
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9/29/2018 3:51pm
AJ565 wrote:
Just watched the video. Sounds like jetting to me. This is the jetting we've found works well in a '18 150 so it should get you...
Just watched the video. Sounds like jetting to me. This is the jetting we've found works well in a '18 150 so it should get you in a better direction.

Pilot 30
470 main
slide 5.5
needle 42-71 3rd clip from a 2019.
I’m really happy with the JD jet kit on my 2016.
dtl210
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9/29/2018 4:00pm
AJ565 wrote:
Just watched the video. Sounds like jetting to me. This is the jetting we've found works well in a '18 150 so it should get you...
Just watched the video. Sounds like jetting to me. This is the jetting we've found works well in a '18 150 so it should get you in a better direction.

Pilot 30
470 main
slide 5.5
needle 42-71 3rd clip from a 2019.
I've tried dozens of jetting combos with no change to the bog. The video on the stand it sounds pretty good. On a track it's much worse, not even rideable, and seems to get worse as the bike heat up.
BR8ES
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9/29/2018 4:15pm
For the price, I would replace the spark plug boot and coil, especially since it was out of spec. Not many more things left to do.
dtl210
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9/29/2018 4:53pm
On the coil the reading was all over the place, So it took it off and sanded the mounting tabs up. After that I got a cosistent reading from the coil, but not within spec. Can't get any reading from the spark plug boot.
So I said f-it and ordered a plug boot, coil and stator. Will replace the boot, then test, coil then test, and hopefully will be able to return the stator.

Will be awesome if all of this was because of the plug boot.
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AJ565
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9/29/2018 5:21pm
dtl210 wrote:
I've tried dozens of jetting combos with no change to the bog. The video on the stand it sounds pretty good. On a track it's much...
I've tried dozens of jetting combos with no change to the bog. The video on the stand it sounds pretty good. On a track it's much worse, not even rideable, and seems to get worse as the bike heat up.
My shifter kart was like that. If it’s too rich it can do that under load.
dtl210
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9/29/2018 5:26pm
dtl210 wrote:
I've tried dozens of jetting combos with no change to the bog. The video on the stand it sounds pretty good. On a track it's much...
I've tried dozens of jetting combos with no change to the bog. The video on the stand it sounds pretty good. On a track it's much worse, not even rideable, and seems to get worse as the bike heat up.
AJ565 wrote:
My shifter kart was like that. If it’s too rich it can do that under load.
I guess I can try leaner, but the plug was light brown with richer jetting than I have now. Most around here are a decent bit richer than me and their bikes seem way better. It's not loading up or smoking at all, no spooge whatsoever. Even after a quick warm up on the stand it runs really clean.
I have a 30 pilot and a 470 main so I'll give it a try.
BR8ES
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9/29/2018 6:20pm
dtl210 wrote:
On the coil the reading was all over the place, So it took it off and sanded the mounting tabs up. After that I got a...
On the coil the reading was all over the place, So it took it off and sanded the mounting tabs up. After that I got a cosistent reading from the coil, but not within spec. Can't get any reading from the spark plug boot.
So I said f-it and ordered a plug boot, coil and stator. Will replace the boot, then test, coil then test, and hopefully will be able to return the stator.

Will be awesome if all of this was because of the plug boot.
That thought crossed my mind...
riv187
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9/30/2018 8:15am
Hi Dt210, I'll try to help you again...I HAVE a TC125. I'm not arm chair guessing. I had the same bog in middle that made the bike dangerous to ride on mx track. I didn't like the bike.I did play with mains and pilots. I installed the V-force to little avail. Went to a Denso IWM27 plug. Then I really started asking reading and going back over notes of other bikes I repaired.
The KTMs are not identical and have better flowing airbox-hence less jetting problem. A WFO rider that never lets off will not feel the problem- they jet for WFO.
Ignition readings are tough to get precise...see the temp reading for resistance?,and your leads can effect that too.
Your PV arms operate smoother than mine since you polished them-but my bike runs great with them from factory and do not hang up.
The solutions are opening up airbox see right and left side. Then the jetting.The slide is tooo rich and make the part throttle stumble bog blubber..Its clear in your video.The PV is RPM sensitive. The crackling rich stumble is at part throttle even thought the revs are up as the bike has no load.
Here's pictures of my modified slide.The peak is 7.2mm. Width is 24.8mm. This is close to a 5.5 slide now. This took 30 minutes with dremel and drum sander. The other jetting is PV-2.25,32.5 pilot,460-500 main(500 in sand),Needle 42-75 1st clip,S-7 nozzle, AS 1/4-1.(1/4 was current setting), 40-1 sunuco 110 with Klotz. I'm at 200 ft,,low 90s now,and 65+% humidity. You maybe at 4000 ft and thinner air which would magnify the rich stock slide. We have high humidity that nullifies the lower altitude. AJ that posted before and slipdog had posts last year that walked through a similar issue on TC250.
My bike runs like enduro model now...smooth excelleration from idle to top. Doesnt drool or foul plug. On the track the 125 races I've been in,I'm always in top 3 too first turn,,and on a twisty slippery track we run at wildwood fl the bike is sweet pulling from down low through midrange to revving like it should. The power delivery has me finishing 2-3 spots better. Some riders that say there bike is fine now...just don't know how good it could be....I hope I haven't wasted my time giving the answer. The slide mod will be night and day better.Good luck







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